Aluminum alloys



Patented July 18, 1939 UNITED STATES PATENT OFFICE ALUMINUM ALLOYS Isamu Igarashi and Goro Kitahara, Fuse, Japan,

assignors to Sumitomo Kinzoku-Kogyo Kabushiki Kalsha, Osaka, Japan No Drawing. Application 'June 20, 1938, Serial 1 No. 214,809. In Japan December 15, 1936 1 Claim.

qnagnesium, manganese, and the rest of alumiv num have been known as having high. tensile strength, but where the utmost strength and durability are required, they were unsuitable for the inner surface of both ends of the strips met, and they were tied up with wires at points '20 mm. from each end, and were left alone, special attention being paid to the middle part of the strips to see whether or not cracks would appear in the course of time.

The results of the above mentioned experinamely, E alloy, Sanders alloy and some representative alloys of the present invention, are presented in the following table.

Composition, percent T us E] T v e o onga i011 strength at 50 mm. crack Cu Zn Mg Mn Ca Cr Al v Kq/mm. Percent l 2. 5 20 0. 5 0. 5 Rest 00 10 Appears within 1 day. 2 8 1.5 0.5 do- 55 15 Do.

3 2 8 1. 5 0. 5 do- 59 14 Do. 4 2 8 i. 5 i. 2 0. 02 0. 25 ..do 59. 6 15 No appearance even after year 5 2 8 1.5 1.5 0.04 0.25 .do- 61.0 14 Do.

0 2.5 10 1.5 1.5 0.05 0.25 -do 60.0 14 Do.

7 2 8 1.5 0.5 0.03 0.30 do. 59.8 15 Do.

use due to their harmful nature of season cracking. This present invention accordingly is to obviate the above mentioned defect and to provide an alloy which is well'adapted for use where non-season cracking is essential.

After a long series of tests and investigation, it was discovered that the addition of 0.05-1% chromium and 0.01-0.2% of calcium to the known alloys, was eifective in eliminating from the alloys the defect of season. cracking without sacrificing their tensile strength. Moreover, these elements are capable of making the grainstructure of the alloys in the cast state much liner and consequentlysive-them the ability to be forged; and these elements have a tendency to increase a fluidity in the molten metal in the refining process. Still further, the presence of not more than 1% cl iron or silicon as impuri ties does not give any-inferior quality to the alloys. The presentinvention accordingly provides aluminum alloys containing 1-3% of copper, 4-20% of zinc, 1-2% of magnesium, 0.1-2% of manganese, 0.01-0.5% of chromium, 0.01-0.2%

of calcium, and less than 1% of iron and silicon as impurities.

With reference to the test pieces which had been properlyquenched and tempered, the tensile tests and the season cracking test were conducted with utmost, care. Strips of 1mm. in thickness, 2 mm. in width, and 200 mm. in length, made of many different aluminum alloys were hardened by heating them up to 450 C. and suddenly cooled in water. After this, they were annealed at a temperature of C. for about 24 hours. Then they werelbent so that Pieces 1 and 2 in the above table represent famous light alloys widely known as E alloy ments, the compositions of the test pieces used,

and- Sanders alloy respectively. Piece 3 is about use in many purposes where high tensile strength and non-season cracking are essential as in case of materials for aeroplane manufacturing.

To make the alloys, three different mother alloys consisting of aluminum and copper, of aluminum and manganese, and of aluminum and chromium should first be prepared, and. these three alloys are melted together. with aluminum, to which are further added magnesium and 'zinc. Experiments show that an addition of 0.01 to 2% of molybdenum or 0.01 to 0.5% of titanium ,to the alloys increases the quality of the alloys to a. large extent.

What we claim is:

Aluminum alloys consisting of 4-20% of zinc, 1-3% of copper, 1-2% of magnesium, 0.1-1.5% of manganese,'0.05-1.0% of chromium, 0.01-2% of molybdenum, 0.01-0.2% of calcium and the rest of aluminum, characterized by ready forgeability and by resistance to season cracking. ISAMU IGARASHI.

GORO KlTAHARA. 

